Numerous underground devices such as water meters, gas meters, valves and so on, use radio telemetry for the transfer of data from the meters and/or valves to a handheld computer, fixed network or other mobile reading technology. When providing radio telemetry for these underground devices it is often necessary to place a telemetry antenna at surface level, e.g. on the lawn, sidewalk driveway, pavement, or atop a utility vault or lidded pit, and/or below grade. The surface level location of the antenna can subject the antenna to severe weather conditions as well as to other open exposure conditions such as harsh chemicals and the footsteps of people and animals. Thus, the unit containing the antenna is desirably small, rugged, weather resistant and has a very low profile.
Units containing the telemetry antennas are usually battery operated and may be randomly placed within a data-collection network. In view of these operating conditions, it is desirable for the telemetry antenna to have high efficiency and a near omni-directional radiation pattern. Further, it is desirable to obtain highly uniform electrical performance from the telemetry antenna when mounted upon various dielectric, metal and combination surfaces. Thus, the use of a shielded electronic housing, a substantial integral ground plane, and a sealed radome are desirably used in combination with the telemetry antenna. Additionally, it is desirable that the telemetry antenna's frequency range have the ability to meet varying domestic and foreign telemetry band allocations by altering tuning and matching elements without multiple component changes and costly tooling alterations. In addition to the above-desired features, it is also desirable that the telemetry antenna system be adapted to excitation at off-axis locations.
Currently, there are no telemetry antenna systems which meet a substantial number of the above-listed desires. Thus, there is a need for a telemetry antenna system that can address many, if not all, of the preferred and desired features.